This invention relates to an ISDN circuit multiplexing system using a multiplexer in which high speed digital and ISDN circuits are installed, and specifically relates to an ISDN circuit multiplexing system in which incoming calls and call control connections are made through the aforementioned ISDN circuit.
Call control data on an ISDN circuit control channel (D-channel) include the call control data for only the channel on the ISDN circuit. No call control data are included for multiplexing ISDN circuit channels. Therefore, when one tries to dynamically use ISDN circuits by allocating a needed band width for outgoing calls from terminals, it is not possible to multiplex a plurality of outgoing calls for transmission (for example, to have a 64 Kbps band transmit four 16 Kbps of compressed voice data). When using a multiplexed ISDN circuit, one has had to install a dedicated control channel within the ISDN circuits independent from the control channel to control calls based on one""s unique data; or one has had to allocate a fixed band for the fixed use of ISDN circuit communication channels.
In the related technology, when one attempts multiplexed use of ISDN circuits by manipulating calls from terminals, a special control channel must be installed, consequently increasing the number of pieces of equipment required for controlling control channels. In addition, an additional band for the aforementioned control channel is required within the ISDN circuits, decreasing operational efficiency; This also complicates multiplex processing with respect to send/receive data control in the control channel.
This invention intends to provide a multiplexing system for ISDN circuits in which call control by means of an ISDN circuit for the voice-grade multiplexed linking does not decrease the multiplex ratio when multiplexers are connected to a communication channel constituted with a high speed digital circuit and an ISDN circuit.
This invention pays an attention to the fact that there is a high speed digital circuit between multiplexers and makes the control channel of the aforementioned high speed digital circuit (Dp-channel) available for multiplexed linking by means of ISDN circuits.
In addition, call control data for transmitting outgoing calls coming from a terminal are dynamically sent/received by the control channel of a high speed digital circuit connecting multiplexers, upon setting up a ISDN circuit communication channel by means of said multiplexers. Also, the control data are constituted in the same manner as the call control data of trunk circuits; the data not related with communication channels are transmitted via a control channel of high speed digital circuits.
The above configuration for the dynamic use of ISDN circuits for outgoing calls coming from terminals eliminates the need for a special control channel, providing inexpensive and efficient multiplexed transmission on ISDN circuits.